Edward Lowe accidentally discovered that clay made an excellent cat litter material and began selling it in bags as "Kitty Litter" in 1947. In the US, cat litter is a $2 billion industry consuming of mined clay annually.
Non-clumping conventional litter Ed Lowe’s discovery of
Kitty Litter was the first large-scale use of
clay (in the form of
Fuller's earth) in litter boxes; previously
sand was used. Clay litter is much more absorbent than sand and is manufactured into large grains or clumps of clay, making it less likely to be tracked from the litter box. The brand name
Kitty Litter has become a
genericized trademark, used by many to denote any type of cat litter. Today, cat litter can be obtained at a variety of retail stores. Non-clumping cat litter is often made of
zeolite,
diatomite and
sepiolite.
Clumping litter Clay s Litter clumps were first developed by using
calcium bentonite clay. This was manufactured in the UK in the 1950s by the Fuller's Earth Union (FEU), which later became a part of Laporte Industries Ltd. Subsequently in America, clumping bentonite was developed in 1984 by biochemist Thomas Nelson. Most are made from granulated
bentonite clay, which clumps together when wet and forms a solid mass separate from the other litter in the box. This solid clumped material can be scooped out and disposed of without changing the entire contents of the litter box. Clumping litter usually also contains
quartz or
diatomaceous earth (sometimes called diatomaceous silica, which causes it to be mistakenly confused with silica gel litter). Because of the clumping effect, the manufacturers usually instruct not to flush clumping litters down the toilet, because it could clog it. Clumping clay cat litters are natural products. Some may also contain naturally occurring
crystalline silica, or silica dust, which in California is treated as a known carcinogen under
Proposition 65. Clay litter is also criticized by the manufacturers of non-clay litter because the components of clay litter are commonly obtained from a
strip mine in an environmentally degrading process. This sort of litter can be toxic to
ferrets, leading to both respiratory and digestive problems.
Non-clay Minerals Technologies offers a clumping cat litter in the form of crystals made of "compacted
baking soda", which in contrast to bentonite is either
dust-free or low-dust, and allegedly "100%
CO2 neutral".
Biodegradable litter Biodegradable litters are made from various plant resources, including pine wood pellets, recycled newspaper, clumping sawdust, Brazilian cassava, pea husk, corn, wheat, walnuts, barley,
soy pulp, and dried orange peels. Each year, more than two million tons of cat litter ends up in landfills in the US alone. Primarily, this is not biodegradable or renewable and adds to the waste burden. Some pet owners prefer biodegradable litters due to its friendliness to the environment. Biodegradable cat litter can also be eliminated completely by safely
composting the used litter at home. Other cat owners can be attracted to the biodegradable litters because of their flushability or deodorizing properties. Some pets, such as those with
asthma or sensitive senses of smell, may also benefit from the reduced dust in some forms of biodegradable litter. Biodegradable litter packaged for cats tends to be more expensive than traditional clay litters, so cost is often not a positive factor in their selection. Most biodegradable litters last longer than the equivalent clay or clumping clay litters. Grain-based animal or poultry feed also provides an economical alternative to products marketed specifically as cat litter. Additionally, most of these forms of litter are recycled from human usage and are thus reusing a waste product as opposed to drawing clay from mines.
Guar gum was the principal clumping agent used in biodegradable cat litter as of 2013, with a clumping rate of 69.8%, while
xanthan gum (73.9%) and
plantago gum (57.5%) were identified in one study as potential alternatives. It is also added to bentonite litter to increase its clumping capacity. In 2020, it was still being used in tests of new wood-based biodegradable litter formulations.
Silica gel litter Silica gel litter, often referred to as "crystal litter", is a porous granular form of
silicon dioxide, has the highest absorbency of any litter, and has excellent moisture control and complete odor elimination for an extended period of time compared to other litters. It is typically prepared through a sol-gel process, which involves the hydrolysis and condensation of silica precursors such as tetraethylorthosilicate (TEOS) or sodium silicate (Na2SiO3). The porous structure of silica gel enables it to trap moisture within its network of interconnected pores, effectively locking away urine and preventing it from spreading or leaking. Moreover, many silica gel litter formulations incorporate activated carbon or other odor-neutralizing compounds, which further enhance the litter's ability to control unpleasant smells. In addition to its physical structure, the chemical composition of silica gel also contributes to its performance as a cat litter. The surface of silica gel is covered with silanol (Si-OH) and siloxane (Si-O-Si) functional groups. These groups interact with water molecules through hydrogen bonding and dipole-dipole interactions, enabling the material to absorb and retain moisture effectively. Some owners praise its absorbency because can absorb liquid and odor for up to 30 days for one healthy normal weight cat. It is important to lightly stir the crystals daily while scooping the solid waste, otherwise urine can pool in the box. When crystal litter is saturated, at the end of 30 days or so, it begins to smell and is visibly saturated (the white crystals have turned slightly yellow). In comparison, over the same time period it may take or more of clay or clumping litter, because it is necessary to replenish the litter that is removed when the clumped urine is scooped out. No replenishing is necessary with silica gel (crystal) litter. ==Types==